Tuning Polyolefin Hydrophilicity to Control Sulfonation Cross-Linking Kinetics for Carbon Synthesis

The use of polyolefins as carbon precursors has gained significant attention due to their low cost, wide availability, and potential for upcycling waste materials. A critical step in this process is using sulfuric acid as the chemical agent for sulfonation-enabled crosslinking of polyolefins, which forms thermally stable networks to allow their effective conversion into carbon upon pyrolysis. However, the hydrophobic nature of most commodity semicrystalline polyolefins often limits acid diffusion, making the reaction sluggish. This work investigates the impact of improving polyolefin hydrophilicity to enhance its sulfonation kinetics. By grafting hydroxyl groups onto the polyolefin backbone, we achieved significant enhancement in reaction efficiency. Specifically, just 2 h of crosslinking enables hydroxyl-functionalized, hydrogenated polybutadiene (hPB) to achieve over 50 wt% carbon yield after carbonization, whereas hPB requires 16 h of crosslinking to reach a comparable yield. These results highlight the significance of polyolefin carbon precursor design in overcoming diffusion limits, accelerating sulfonation kinetics, and improving carbon conversion efficiency, further advancing their use for carbon material production.